Combination lock

ABSTRACT

A combination lock of the type having a hollow base (1) containing a central plunger (12) guided for both rotational and slidable movement therein, the base (11) having a plurality of base notches (26) selectively engageable by lock plungers (31) carried by the central plunger (12) for axial movement, each lock plunger (31) having a portion capable of being contained within a respective notch (26) to thereby inhibit rotation, each lock plunger (31) also having a notch (33) arranged, when correctly positioned, to permit rotation of the central plunger (12), and a selection knob (42) which is rotational and slidable with respect to the central plunger (12) and which has a push pin (43) operable to depress selected ones of the lock plungers (31), the central knob (42) obscuring the lock plungers (31) such that it is not apparent which of the lock plungers are the selected ones for a combination.

This invention relates to a combination lock of the same general typedescribed in the specification which accompanied our (now abandoned, butpublished) Australian Patent Application No. 77731/81 dated the Nov. 20,1981.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In that said specification there was described a combination type lockhaving a hollow base containing a central plunger, bearing surfacesbetween the base and central plunger guiding the plunger both forrotational and slidable movement, an annulus carried by the base andhaving a plurality of notches in a peripheral edge, a plurality of lockplungers carried by the central plunger for movement relative thereto inan axial direction, each lock plunger having a portion of its surfacecapable of being contained within a respective annulus notch whichthereby inhibits rotation of the central plunger, but each lock plungeralso having a notch intermediate its ends arranged that, upon selectivedepression of the lock plungers from initial positions, all of the lockplunger notches lie in the same plane as the annulus such that the lockplungers cause to inhibit rotation of the central plunger, and means toreset the lock plungers to their initial position.

2. Description of the Prior Art

A data bank search revealed also U.S. Pat. No. 4,191,035 HATCH; U.K.Patent No. 1,530,861 STANDEN; and U.S. Pat. Nos. 3,937,046 WANG;3,910,078 S-B MANUFACTURING CO. LTD.; 4,176,533 NORDENDALE; 4,274,272WANG; 4,266,415 CLARKE; and U.K. patent Nos. 1,566,017 MILLIKEN and1,503,526 DANILIN. Of these, the most pertinent appear to be HATCH andSTANDEN, but in all prior art known to the applicants, the ends of thelock plungers were visible from the exterior of the lock, and althoughextremely difficult to pick, it is nevertheless still possible to picksuch a lock, and this possibility increases with age as some of the lockplungers would appear more polished than others due to consistent use.

BRIEF SUMMARY OF THE INVENTION

The main object of this invention is to provide further improvementswhich will still further increase the difficulties of picking acombination lock of the type described, and in an embodiment of thisinvention a combination lock of the type generally described in thatsaid specification is further characterised by a selection knob whichextends over the lock plungers to obscure them, the selection knob beingguided for rotational and axially slidable movement with respect to thecentral plunger, and having a push pin by which it can selectivelydepress the lock plungers.

More specifically, this invention consists of improvements in acombination type lock having a hollow base containing a central plungerguided for both rotational and slidable movement therein, a circularsurface fixed with respect to the base and having a plurality of notchestherein, a plurality of lock plungers carried by the central plunger formovement relative thereto in an axial direction, each said lock plungerhaving a portion of its surface capable of being contained within arespective said base notch to thereby inhibit rotation of the centralplunger but each said lock plunger also having a notch, so arranged thatthere is a plane which, if all said plunger notches lie therein, thelock plungers cease to inhibit rotation, said improvements comprising aselection knob obscuring the lock plungers, means guiding the selectionknob for rotational and axial slidable movement with respect to thecentral plunger, and a push pin carried by the selection knob operableto selectively depress said lock plungers.

It is important that the lock should not be readily breakable such that,by merely shearing the lock plungers, the central plunger becomesrotatable and thereby can operate a lock. In another embodment of thisinvention each of at least some of the lock plungers is provided with apair of spaced notches, one of which extends to its inner end and isengageable with a cylindrical surface, each notch having a flat surfacewhich divides the respective lock plunger into a semi-circular portion,and this arrangement maintains better strength than the arrangementwhich was described in our earlier said application.

BRIEF DESCRIPTION OF THE DRAWING

An embodiment of the invention is described hereunder in some detailwith reference to, and is illustrated in, the accompanying drawings, inwhich:

FIG. 1 is an "exploded" elevational section through a lock,

FIG. 2 is a section taken on line 2--2 of FIG. 1,

FIG. 3 is a plan view of base 11 taken on line 3--3 of FIG. 1,

FIG. 4 is a section similar to FIG. 1, but showing the elements of thelock assembled with the central plunger depressed to a "reset"position;,

FIG. 5 is a diagrammatic "stretch-out" showing how the lock plungernotches can be selectively positioned to lie in a single plane whichallows rotation of the central plunger,

FIG. 6 is a fragmentary section corresponding to FIG. 4 but drawn to anenlarged scale, and

FIG. 7 is a section taken on line 7--7 of FIG. 4, to a larger scale, andshowing how the lock plungers function to inhibit rotation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this embodiment a combination lock 10 has a hollow cup-like base 11with a central plunger 12 therein. The base 11 contains two internalplunger guide surfaces, the lower one 14 of which guides a stem 15 ofthe central plunger 12 and the upper one 16 of which guides an outercylindrical surface 17 of the intermediate portion 20 of the centralplunger 12. The central plunger 12 is movable within the base both forrotational movement and for sliding movement against base spring 18, butthe uppermost portion of the central plunger 12 is a larger diameterportion 19 than intermediate portion 20 and between the uppermostportion 19 and the intermediate portion 20 is a shoulder 21 which, uponinward (reset) movement of the central plunger 12, abuts the upper andouter end of the cup-like base 11 to arrest such movement.

The base 11 also has an inwardly directed annulus 24 which projectsradially inwardly from its skirt 25, the annulus having a plurality ofpart-round notches 26 which extend radially outwardly from its innerperipheral edge 27, the base notches 26 being arranged to subdivide apitch circle equally, except for one "blank" space (designated 28 inFIG. 3) where no notch exists.

A plurality of lock plungers 31 are carried in apertures 29 in thecentral plunger 12, the upper portions of the lock plungers beingcontained by aperture walls in the central plunger which are similarlyarranged on a pitch circle except for the one blank space 28, so thatwhen co-axially aligned, the apertures of the plunger can also bealigned with the half round notches 26 of the cup-like base 11.

Each of some of the lock plungers 31 within the central base is providedwith a pair of plunger notches 33, the lower notch 33 extending to theinner end and having a flat surface which divides that lower end into asemi-circular portion (FIG. 7), and the other (upper) notch anintermediate notch outward of the lower notch, again dividing theplunger into another semi-circular portion, and each lock plunger 31also has a pair of circular grooves 34 which selectively engageresilient means (a spring loaded ball 35) within the central plunger 12so that each lock plunger can snap into one of two alternativepositions.

The projection 38 which exists between the two notches 33 of each lockplunger 31 is arranged so that it can either be in the same plane as thebase annulus 24, or between the base annulus 24 and a reset surface 39which is co-axial with the annulus and has the same diameter, in such away that the lock plunger can occupy only one position where its notchesallow free rotational movement with respect to the annulus. However,some of the lock plungers 31, (as shown in FIG. 5), do not haveprojections, but are provided with one notch only, so that, ifincorrectly depressed, they prohibit rotation of the central plunger.FIG. 7 illustrates three such conditions in the full black circles.

There is provided a cup-like selection knob 42 having a skirt 22surrounding larger diameter portion 19 of plunger 12, and also havingwith a push pin 43 depending from an inner flat surface, the push pinbeing selectively aligned with any one of the lock plungers 31 orpositionable over the blank area. When positioned over the blank areadepression of the selection knob urges the central plunger 12 inwardlyagainst spring 18, whereupon the inner ends of lock plungers 31 abut thereset surface 39, returning the lock plungers 31 to an original position(FIG. 4). The selection knob 42 is retained for both its axial androtational movement by the head 44 of a threaded stem 45 which containsa female thread engageable by an elongate screw threaded member 46 whichfastens through the lock assembly. The lower end of the central plungerstem is bifurcate at 47, and this provides means for controlling theopening or closing of a lock catch, the surfaces defining the bifurcateportion 47 engaging the catch in a manner similar to that in common lockcatches. There is also provided a "C" spring 48 contained within agroove in the lower end of the stem for retention of the central plungerto the cup-like base. A return spring 50 urges selector knob 42 axiallyoutwardly.

In use, the selector knob is positioned above one of the lock plungerswhich needs to be pushed inwardly for its upper notch 33 to align withthe base annulus 24. The selection knob is then pushed inwardly againstspring 50, and its push pin pushes that lock plunger downwardly into therequired position. Spring 50 will be fully depressed before spring 18commences its compression. The selection knob is then released, androtated to be positioned above another lock plunger, and this action isrepeated three or four times. There can for example be 10 lock plungers(pins). When all the lock plungers are correctly positioned and theselection knob is aligned over any plunger that is depressed, theselection knob is able to be depressed engaging the inner cylinder andthis in turn will allow the door to be opened by rotating the selectionknob. However, depressing of any one of the "incorrect" lock plungers 31will result in inhibition of rotation of the central plunger 12.

Thus, for example, to unlock a door with a combination (1,2,3), thefollowing steps are taken:

1. Turn selection knob to zero (or blank) position and depress (toclear), compressing both the return spring 50 and the base spring 18 sothat the lock plungers all move outwardly towards the knob.

2. Turn selection knob to position one (one click clockwise) anddepress. (The "clicks" are felt as push pin 43 rides over the upper endsof respective apertures 29 in plunger 12, when selection knob 42 ispushed in for part only of its axial travel against spring 50, and thenrotated.

3. Repeat over position two and three.

4. With selection knob depressed over pin three, so that push pin 43engages a part round notch 26, turning the knob also turns the centralplunger 12, and opens the door.

5. To re-lock turn selection knob to zero (or blank) and depress whichresets all pins in outward position. This cannot be achieved unlessselection knob is at zero, as the knob's pin will abut on the lockingpins.

We claim:
 1. In a combination type lock having a hollow base containinga central plunger, a reset surface on the base, a circular surface fixedwith respect to the base and having a plurality of notches therein, aplurality of lock plungers carried by the central plunger for movementrelative thereto in an axial direction, each said lock plunger having aportion capable of being contained within a respective said base notchto thereby inhibit rotation of the central plunger but each said lockplunger also having a notch, so arranged that there is a plane which, ifall said plunger notches lie therein, the lock plungers cease to inhibitrotation,improvements whereby the lock plungers are equally spaced fromone another on a pitch circle, except for one blank space, said centralplunger being guided for both rotational and slidable movement in thehollow base, a selection knob obscuring the lock plungers, means guidingthe selection knob for rotational and axial slidable movement withrespect to the central plunger, and a push pin carried by the selectionknob operable to selectively depress said lock plungers, but whenlocated over said blank space, said push pin being operable to depresssaid central plunger together with said lock plungers, abutting the lockplungers against the reset surface, and thereby effect reset of the lockplungers in said central plunger.
 2. Improvements in a combination typelock according to claim 1 wherein said circular surface is the innerperipheral surface of an inwardly directed annulus carried by the base.3. Improvements in a combination type lock according to claim 1 or claim2 wherein said selection knob is a cup-like member having a skirt whichpartly shrouds the central plunger.
 4. Improvements in a combinationtype lock according to claim 3 wherein a push member comprises a pincarried by the cup-like member and directed inwardly, and positionableabove each of the lock plungers and said blank space in turn uponrotation of the selection knob.
 5. Improvements in a combination typelock according to claim 1 further comprising a knob return springlocated between the selection knob and the central plunger. 6.Improvements in a combination type lock according to claim 5 furthercomprising a base spring between the central plunger and the base whichis stiffer than the knob return spring.
 7. Improvements in combinationtype lock according to claim 1 wherein the central plunger has a stemwhich extends through the base, and further comprising a headed stemwhich extends through the selection knob, the head of which constrainsaxial sliding movement of the selection knob, and a fastener extendingthrough the central plunger releasably retaining the headed stem to thecentral plunger.